Louver system with sandwich type blades

ABSTRACT

A louver system to be used on spacecrafts and space vehicles, comprising movable panels mounted on a support means, each being adapted to rotate about an axis parallel to the surface of the support means, and actuators sensitive to the temperature of said support means for moving the panels about their respective axis. Each panel consists of two substantially parallel blades that are not in thermal contact with each other, the outer surfaces of the two blades having high reflectance and thermal emissivity factors and the two inner surfaces thereof which are facing each other having a low emissivity factor.

United States Patent 1 Janes LOUVER SYSTEM WITH SANDWICH TYPE BLADES[75] Inventor: Manfred Janes,Voorschoten, Netherlands [22] Filed: Jan.20, 1972 [21] Appl. No.2 219,232

[30] Foreign Application Priority Data Jan. 26, 1971 Belgium 98974 [52]US. Cl. 244/1 SC, 49/1, 160/1, 244/1 SS 51 Km. Cl. 864g 1/10 [58] Fieldof Search 244/1 SS, 1 SC; 136/89, 86 R; 160/1, 236; 49/1, 25, 74-,

[56] References Cited UNITED STATES PATENTS 3,031,351 4/1962 Mcllvaine250/237 R 3,110,936 11/1963 Berard 160/236 X 3,290,823 12/1966 Okumoto160/236 X 3,441,444 4/1969 Chesner et al. 136/86 R PrimaryExaminer-Milton Buchler Assistant ExaminerBarry L. KelmachterAttorney-Milton J. Wayne et al.

[57] ABSTRACT A louver system to be used on spacecrafts and spacevehicles, comprising movable panels mounted on a support means, eachbeing adapted to rotate about an axis parallel to the surface of thesupport means, and actuators sensitive to the temperature of saidsupport means for moving the panels about their respective axis. Eachpanel consists of two substantially parallel blades that are not inthermal contact with each other, the outer surfaces of the two bladeshaving high reflectance and thermal emissivity factors and the two innersurfaces thereof which are facing each other having a low emissivityfactor.

2 Claims, 2 Drawing Figures Patented Oct. 30, 1973 FIG. 2

LOUVER SYSTEM WITH SANDWICH TYPE BLADES The present invention relates toa louver system intended for being used on spacecrafts and spacevehicles.

Louver systems are used to control the skin temperature of spacecraftsand space vehicles during their mission and to maintain it withinprescribed limits. Such systems usually comprise movable panels mountedon a base plate comprised of the outer skin of the spacecraft or spacevehicle or on a support member placed inside thereof, said panels beingoperated by suitable actuators. The latter are temperature sensitiveelements such as bimetal blades which are effective to change the panelorientation i.e. their opening angle depending on the base platetemperature (support member or outer skin). The higher said temperature,the wider the opening angle. The actuation of the panels may be effectedin any conventional manner, such as, for example, by means of the typedisclosed in [1.8. Pat. No. 3,441,444. This patent also discloses asupport structure for louvers.

The prior art louver systems are only capable of operating in the shadesince they have detrimental effects in full sunshine. When the panelsare in a partially opened position, they are trapping sunlightthereunder, thereby causing the vehicle skin temperature to increasedangerously.

To obviate this drawback it would have been possible to provide thelouver panels with a reflecting coating. However, when the vehicleorientation is such that the panels are in the shade, said coating wouldact as a thermal barrier to radiation.

The foregoing problem is solved by the arrangement of the inventionwhich is capable of operating in the shade as well as in full sunshine.

This invention comprises louver panels each consisting of twosubstantially parallel blades that are not in thermal contact with eachother. The outer surfaces of the two blades have high reflectance andthermal emissivity factors and the two inner surfaces thereof which arefacing each other have a low emissivity factor.

According to a particular embodiment each louver blade comprises a firstlayer of transparent material and a second layer made of a metaldeposited onto a surface of said first layer; and the second layers ofthe two louver blades are facing each other.

The surface of the base plate which is facing the louver panels cancomprise a reflecting layer having a structure similar to that of thelouver blades.

The above and other features of this invention will be apparent from thefollowing description which is to be read in connection with theaccompanying drawings, wherein FIG. 1 is a schematic sectional view of alouver system embodying the invention;

FIG. 2 is a sectional view showing the blade structure of the invention.

Referring to FIG. 1 there is shown in cross-sectional view a portion ofa base plate 1 having movable louver panels such as 2 mounted thereon,said panels being respectively rotatably mounted on a plurality of axes3 that are parallel to the outer surface of base plate 1. As mentionedabove, the base plate can be mounted inside of the vehicle or on thewall thereof. The panels 2 are operated through actuators (not shown)which are sensitive to the base plate temperature.

According to the invention, each movable panel 2 comprises two parallelblades 4 and 5 each of which has an outer layer 6 and an inner layer 7and which are mounted on both sides of the rotation axis 3 and arespaced from each other so as not to be in thermal contact with eachother. The two outer layers 6 have high reflectance and emissivityfactors whereas the two inner layers 7 which are facing each other havea low emissivity factor.

More specifically, as shown in FIG. 2, each outer blade layer 6comprises a substrate made of a transparent material such as quartz, andthe inner layer 7 is formed of metal such as silver or aluminum forinstance. The metal layer 7 can be vapor deposited onto substrate 6. Acharacteristic feature of this louver structure is that the two outerpanel layers 6 are thermally decoupled and that the two layers 6 and 7fulfil two different functions as will be apparent from the disclosureto follow.

Heretofore it was assumed that the internal thermal conductance of thelouver panels is or may be considered as isothermal. The inventioncancels said assumption out. The outer louver surface which lookstowards space when the panels are in a closed position takes over thefunction of a solar reflecting skin. Incident radiation from space isreflected on outer layer 6 of any louver panel as shown by incidentradiation a in FIG. 2. In addition, since the outer layer 6 has a highemissivity value, it emits thermal energy as indicated by arrows 1 onFIG. 2, thereby causing its temperature to be lower than that of theother layer 7. In this way there is a temperature gradient which isnegative in the direction towards space such that in effectsubstantially no energy from space can enter the louver system. The highemittance of the louver blade layer 6 facing the base plate when thelouver panel is in a closed position and the base plate itself causesenergy exchange to occur between these two surfaces in the wavelengthregion of the thermal radiation so that the temperature of both surfacesof layer 6 and base plate I can be assumed to be substantially equal aslong as the louver system is in a fully closed position.

The low emittance of both inner layers 7 causes the two outer layers 6to be substantially completely thermally decoupled. Energy loss is thusprevented as long as the louver system is in a closed position. In thisway the vehicles wall temperature can be strictly controlled andmaintained within prescribed limits. The temperature range wherein thesystem can operate, i.e., while maintaining the vehicles walltemperature within the prescribed limits, is determined by selecting thesuitable emissivity values for the inner layers 7.

' When the louver panels are in a partially opened position, incidentradiation from space is reflected on the two blades 4 and 5. The baseplate is then impinged by a part of said reflected radiation as shown byradiation indications b and c on FIG. 1, as well as by radiationdirectly incident from space such as radiation indication d on FIG. 1.To protect the base plate against radiation, there is provided thereon areflecting skin 8 (see FIG. 1) similar to the metal layer blades 4 and5. In this way, incident radiation is reflected towards space, possiblyafter having been reflected several times between reflecting louverblades and base plate. Due to the high emittance of the outer wall ofbase plate, this emits thermal energy directly towards space and thetemperature thereof is thus reduced.

The device thus realized permits an efficient temperature control of thewalls of spacecrafts and space vehicles to be achieved in full sunshineas well as in the shade.

It is to be understood that the invention is not limited to theparticular embodiments described hereinbefore and that many changes andvariations can be made by those skilled in the art. For example, one ormore intermediate layers can be provided between transparent substrate 6and metai layer 7, said intermediate layers being made for instance of ametal compound such as ZrO or Mglin order to increase reflectance of themetal layer.

What is claimed is:

I. In a spacecraft of the type having a surface, a plurality of louverpanels mounted for rotation about paraliel axes adjacent said surfacewith said axes being parallel to said surface, and thermally responsivemeans for controlling the angular displacement of said panels abouttheir respective axes; the improvement wherein each said panel iscomprised of a pair of substantially parallel blades spaced apart so asnot to be in thermal contact with each other, the axis of rotation ofeach said pair of blades being vertically disposed between the blades ofeach pair of blades, each blade of each said pair of blades having onesurface with high reflectance and emissivity factors, the blades of eachpair of blades being mounted with the low emissivity surfaces facingeach other, and wherein said surface of said spacecraft is reflective.

2. The spacecraft of claim 1 wherein each said blade is comprised of alayer of transparent material forming the surface thereof having highreflectance and emissivity characteristics, and a layer of a metaldeposited on said transparent material and forming said surface with lowemissivity factor.

1. In a spacecraft of the type having a surface, a plurality of louverpanels mounted for rotation about parallel axes adjacent said surfacewith said axes being parallel to said surface, and thermally responsivemeans for controlling the angular displacement of said panels abouttheir respective axes; the improvement wherein each said panel iscomprised of a pair of substantially parallel blades spaced apart so asnot to be in thermal contact with each other, the axis of rotation ofeach said pair of blades being vertically disposed between the blades ofeach pair of blades, each blade of each said pair of blades having onesurface with high reflectance and emissivity factors, the blades of eachpair of blades being mounted with the low emissivity surfaces facingeach other, and wherein said surface of said spacecraft is reflective.2. The spacecraft of claim 1 wherein each said blade is comprised of alayer of transparent material forming the surface thereof having highreflectance and emissivity characteristics, and a layer of a metaldeposited on said transparent material and forming said surface with lowemissivity factor.